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From YouTube: OpenShift 4.x Ignition
Description
In this video blog, we will review the cluster bootstrap process in detail and understand how ignition works for RHCOS nodes. It will give you detailed overview of how the nodes get started on an OCP 4.x cluster.
For more information, please visit openshift.com
A
Hello,
welcome
back
to
open
shop
for
tekserve,
deep
dive,
video
series
in
this
video,
we'll
talk
about
the
cluster
installation
and
ignition.
We
cover
clustered
installation
in
our
first
video,
but
we'll
get
a
little
bit
deeper
in
this
video
so
that
it
sets
us
context
for
talking
about
ignition
process.
Let's
revisit
the
cluster
installation
process,
the
bootstrap
process,
OpenShift
installer,
creates
a
bootstrap
node.
First,
this
bootstrap
node,
beginning
with
open
shift
4.4
comes
up
with
an
instance
of
its
CD
of
its
own.
A
This
food
shop
node
also
hosts
remote
resources
that
are
required
for
masters
to
come
up
these
remote
resources.
Our
ignition
configuration
files
we'll
talk
about
in
a
few
minutes.
The
bootstrap
node
now
starts
a
temporary
kubernetes
control
plane
and
runs
a
HDD
operator.
It
uses
that
HCD
operator
to
scale
up
the
HDD
to
three
instances
by
using
master
hosts
and
it
forms
an
HDD
cluster,
the
temporary
control
plane.
Eventually,
she
could
use
a
production
control
plane
on
the
master
machines
and
it's
CD
is
now
transferred
onto
the
master
machines.
A
The
bootstrap
node
injects
openshift
specific
components
into
the
newly
formed
control
plane
and
the
temporary
control
plane
shuts
down
yielding
to
the
production
control
plane.
So
the
installer
takes
down
the
bootstrap
node,
but
if
you're
using
user
provision
installation,
then
you
have
to
tear
down
the
bootstrap
node.
Now
the
master
hosts
will
host
the
remote
resources
or
the
ignition
file
for
masters,
as
well
as
the
workers,
so
the
worker
machines
that
will
come
up
either
now
or
in
the
future
will
fetch
those
remote
resources
from
the
master
machine
and
they'll
finish.
A
Booting
I
wanted
us
to
quickly
review
this
bootstrap
process
and
have
it
freshen
or
more.
We
get
into
the
ignition
process
that
we
are
going
to
discuss
now.
Ignition
is
a
provisioning
utility.
It
is
designed
specifically
for
Red
Hat
core
OS.
It
is
used
for
manipulating
the
disks
during
early
boot,
that
is
during
the
initrah
methis.
You
can
use
it
for
partitioning
disk
formatting
partitions
writing
files.
A
This
could
be
like
system
D
units,
Network
D
units
and
things
like
that,
or
even
configuring
users
ignition
reads
its
configuration
from
a
source
and
this
source
could
be
a
remote
URL.
It
could
be
network
metadata
surveys
or
things
like
that,
and
it
applies
that
configuration
on
the
top
of
the
core
OS
image
that
you
download
from
Red
Hat.
So
even
though
ignition
runs
only
once
it
does
a
lot
of
things,
it
runs
very
early
in
the
boot
process
and
it
is
able
to
accomplish
the
configuration
before
the
user.
A
Space
begins
to
boot
up
so
spinning
up
of
a
new
core
OS
machine.
For
the
first
time
it
involves
pulling
the
Red
Hat
Carozza
me
from
Red
Hat,
and
you
apply
the
ignition
configuration
coming
from
the
ignition
file
when
you
run
openshift
installer,
it
generates
boots
traffic,
Nishant
file,
master
ignition
file
and
the
worker
admission
file,
which
provides
the
configurations
for
the
respective
machines
master
ignition
file
is
initially
hosted
by
the
bootstrap
server
and
later
the
Masters
will
host
the
master
ignition
file
and
the
worker
ignition
files
master
runs
the
machine
config
server.
A
That'll
have
the
machine
configurations.
We
will
talk
about
machine
config
server
a
little
later,
let's
go
through
the
ignition
process.
First,
so,
let's
see
how
the
nodes
spin
up
for
the
first
time
as
I
said
before
the
bootstrap
ignition
file
gets
generated
by
the
openshift
installer.
You
will
see
this
better
if
you
are
doing
a
bare
metal
installation
all
this
process
that
I
am
explaining
is
all
under
the
covers
when
you
run
openshift
installer
on
a
cloud.
A
But
if
you
are
doing
bare
machine
installation,
you
will
see
this
step-by-step
boot
chef
ignition
file
is
supplied
as
a
kernel
parameter.
While
you
are
bringing
up
the
bootstrap
machine.
This
is
for
the
first
time.
This
boots
have
ignition
file
about
1300
lines,
and
it
includes
their
configurations
not
just
for
the
bootstrap
machine,
but
also
for
master
and
workers.
Once
the
booster
machine
comes
up
that
hosts
the
Machine
configurations
for
master,
that
means
the
ignition
configure
for
the
master
is
hosted
by
the
bootstrap
machine.
A
Now,
the
open,
shipped
installer
would
have
also
generated
a
master
ignition
file.
This
is
a
small
file
and
you
can
make
some
customizations
to
that
and
you
can
mount
that
master
ignition
file
as
a
kernel
parameter
and
that
master
ignition
file
is
merged
with
the
bigger
master
ignition
file
that
is
served
by
the
bootstrap
machine.
A
That
combined
ignition
is
applied
so
again,
just
like
the
bootstrap
machine,
core
OS
image
comes
from
Red
Hat
and
you
will
be
supplying
the
core
OS
image
with
the
customizations
that
the
ignition
provides
once
the
master
comes
up,
master
will
host
a
machine
config
server
that
renders
the
ignition
configuration
files
for
both
master
and
worker,
so
you'll
have
master
dot,
AGN
and
worker
dot
idea.
If
you
remember
the
installation
process
that
we
discussed
before
once
the
masters
come
up
and
take
over
the
control
plane,
the
bootstrap
will
cease
to
exist,
so
it
can
be
shutdown.
A
So
when
the
worker
tries
to
come
up
again,
you
have
the
worker
ignition
file
that
comes
from
the
Installer
that
will
be
merged
with
the
worker
ignition
file
hosted
by
the
master,
and
that
gives
you
the
combined
ignition
file
that
will
be
used
for
workers
to
come
up.
Every
host
pulls
this
ignition
file
and
it
applies
that
on
the
Red
Hat
Kouros
image.
This
is
how
the
ignition
configuration
works,
and
this
is
how
the
nodes
will
come
up
for
the
first
time.
You
can
observe
this
during
the
bare
metal
installation.
A
I
am
showing
you
the
documentation
for
bare
metal
installation.
You
first
create
the
ignition
config
files
by
running
this
command,
and
then
you
use
the
ignition
configuration
file
and
supply
that
as
kernel
parameter.
So
to
summarize,
in
this
video
we
reviewed
the
cluster
installation
process.
We
discussed
the
ignition
process
where
the
ignition
file
supplies
the
configurations
which
are
applied
on
the
Red
Hat
image.
We
also
discussed
in
detail
on
how
the
ignition
process
works
when
the
nodes
spin
up
for
the
first
time
during
cluster
installation
in
the
upcoming
videos.